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A123800
Number of ways to build a contiguous building with n LEGO blocks of size 1 X 6 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position.
0
11, 136, 1991, 30701, 500038, 8346595, 142812582, 2481290457, 43703296703
OFFSET
1,1
COMMENTS
The base block is not counted among the n and must be the only block in the bottom layer of the building.
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Søren Eilers, Oct 29 2006
STATUS
approved